Radio repeater system



RADI O REPEATER SYSTEM M5 E www.

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W T TORNE Y Patented Nov. 23, i926o i l restan raranr rica.

UNITED STATES DE LOSS K. MARTIN, OF WEST ORANGE, NEVI JERSEY, ASSIGNORTO AMERCANTELE- PHONE ANI) TELEGRAPH COMPANY, A. CORPORATION 0F NEX/VYORK.

RADIO REPEATER SYSTEM.

Application filed March 22, 1924.

This invention relates to radio signaling systems, and particularly to amethod and means for operating a system employing one or more repeaterstations between the terminal stations thereof, which method ischaracterized by the changing` of the frequencies of the received wavesat each repeater station in accordance with a definite plan, wherebysinging of individual repeaters or between repeater stations or with aterminal station may be prevented, and whereby the number of frequenciesper channel does not exceed a predetermined number `irrespective of thenumber of repeater stations.

In the operation of a long distance radio system having one or morerepeaters between the terminal stations thereof, it has heretofore beennecessary to change each received frequency of each transmission channelat each repeat-orto a different frequency in order to prevent currentstransmitted from the same repeater from entering the receiving circuitsthereof or the receiving circuits of other channels at a distantrepeater or terminal station. For a system without repeaters, twofrequencies are normally required for each two-way channel, one fortransmitting in one direction and another for transmitting in theopposite direction. Considering. for the purpose of illustration, asystem of the prior art having two terminal stations and a singlerepeater therebetween, if we transmit from one terminal a frequency f,and from the other a frequency 2, singing may be prevented only bychanging at the repeater the frequency #to a third frequency such as f.,before radiating` it therefrom to the distant terminal to which it isintended to go; and similarly, by changing the frequency y, to a fourthfrequency such .as f4 before radiating it therefrom. While singing willthereby be avoided bot-h at the repeater station and also with theterminal stations, it is obvious that. this result is obtained only by aliberal use of the frequency spectrum since the system requires fourfrequencies to effect two-way transmission between terminal stations ofa system involving only one repeater. lf two or more repeaters areincluded in such a system, the number of frequencies required for thesystem will, in general, be increased two per channell for eachrepeater. Obviously, the

serial No. 701,188.

large demand made upon the frequency spectrum by such a system greatlyreduces the field of use of radio repeaters. rllhe applicant has foundthat by the use of means for controlling the direction of transmissienand the reception of waves of the various frequencies and means forchanging and selecting the frequencies, it is possible to greatly reducethe number of frequencies required by a multi-repeater radio systembelow the number given above, namely, two per channel per repeater.

In my copending application, Serial No. 701,186 filed March 22, i924, ldisclose a method and means for operating a radio communication systeminvolving the use of repeaters, in which system the number offrequencies per channel of communication does not exceed four,regardless of the number of repeaters involved. rlhe system disclosed inthe said copending application is characterized by the recepten at anyrepeater station of waves from both directions at different frequencies,and by transmitting therefrom in both directions at dif` ferentfrequencies the reception frequencies lying within one side 'band of acontrolling` carrier frequency and the transmtting frequencies lyingwithin the opposite side band of that carrier frequency. y

rllhe object of the present-invention is to provide a method foroperating a two-way radio communication system involving a plurality ofrepeaters, in which the number of frequencies per channel ofcommunication does not exceed four, regardless of the number ofrepeaters involved, which method is characterized by reception at anyrepeater station from opposite directions at different frequencies; andfor transmitting` from that repeater station in opposite directions alsoat different frequencies, the received waves lying` within `oppositeside bands of a fictitious carrier frequency and the transmitted waveslikewise lying within opposite side bands of that same carrierfrequency.

The invention will be clearly understood from the following vdescriptionwhen read in connection with the attached drawing, of which Figure 1shows schematically one form of embodiment of the invention, Fig. 2shows directional characteristics of the receiving antennae of arepeater station, and Figs. 3 to 5 inclusive represent various Cilmethods of frequency distribution throughout a system employing theapparatus shown in Fig. l.

Fig. l shoivs primarily the circuit arrangement in` schematicl forni ofone of the rcpeater stations as for example, RRl indi cated upon thefrequency distribution charts shown in Figs. 3 to 5 inclusive; andincidentally, the west terminal station and also part of the receivinglcircuit of the adjacent repeater station RRZ. The West station, whichmay be of any Well known type, coinprises a transmitting antenna TA1,adapted to transmit, for example, theV frequency f5 of Fig..3. It mayalso be designed and adjustn ed to transmit a frequency A f1, whichlatter frequency is used for modulating the signaling frequencies at therepeater stations. It may be prefe lable to provide a separatetransmitting antenna in connection with the system for transmitting thismodulating frequency and such an antenna is shown in Fig. 1 by Tr .5, orA fi may be supplied locally at each repeater by means of an oscillatorgenerating the frequency A f1. ri`he west stationy also comprises areceiving` antenna BA1, Which is designed and1 adjusted for thereception of signals coming` from the east. It is to be understood thatthe terms east an( West have been chosen arbitrarily to describe thisinvention and constitute no limitation therein.

At the radio repeating station BB1 each of the-receiving antennae BA,and RAQ, is designed andI adjusted in ways Well lincivn tothose skilledin the art for receivingsia'- nals efficiently from one direction only.lt is Well known that an antenna structure comprising a verticalantenna, such as l and a loop such as 2, may have directionalcharacteristics, such as shoivn in. F 2. That is tosay, by the properadjustment of the constants vof. each antenna circuit and by properorientation of the loop, the combined structure may be caused to receivemost etlicient-ly from one direction only, as shovvn inl Fig. 2. Forexample,` the antenna RA2 may be adjusted to receivel efficiently fromthe West.; that iste-say, signals of 'the frequency transmitted by theantenna TA1 and the antenna structure RAg may, in like manner, beadjusted to receive etliciently fromA the east, that is to say, thefrequency f3` transmitt-edv from one of the transmitting antennaeassociated With the repeater Which repeater should preferably be similarinV arrangement to the repeater RR. B means ofthe condensers 3 and. 6the loops 2 and' 5 maybe properly tuned for the frequencies` that theyare to receive. M, and i/i'z` are modulators inn'hich the received sic--naling frequencies are beaten with another frequency, which may betermed the medir latin?,` frequency. received from the antenna TA5. Acontrolling device C adjusts the frequency, if necessary, that is to beapplied to the modulating devices and an amplifier ^r3 aniiplilies thismodulating frequency be- 'ore impressing ,it upon the modulators. F1. L,F3 and FL are filters for selecting the frequencies that are intended topass Ythrough these translating circuits. A1v and Ag are amplifiers'Whose output sides are connected 'th the transmitting antenntc 'llAgand TA1, respectively. rlhe antenna iAI transmits the frequency selectedby the filter FJ; to the receiving antenna structure ltr/lr.A of therepeater Rit-2. The tiansmitting` antenna TA,g is intended to transmitthe frequency selected by the filter FLL to the receiving antenna o BA1connected with the West terminal station.

Figs. 3, l and 5 represent different ways of distributing thefrequencies throughout a communication systen'i, such as is shownschematically in Fig.. l, which will prevent singing at the repeaters orbetween a repeater and a terminal station. In Figs. 23 and 4i, thefrequencies received at cach repeater station are translated a definitefrequency interval Within the same side band and are then transmitted.ln Fig. the received frequencies are translated aV definite frequencyinterval A f, into the opposite side band. of a fictitious carrierfrequency f. rlhe method of operating the system of Fig. l in order tocarry out the method shown in Fig. 3 is as follows: The frequency f5Would be transmitted by the antenna Tftlr to the receiving` antenna RAZ,Which would be adjusted to have the reception characteristie shown bythe left-hand diagram of Fig. 2. This characteristic indicates goodreception from the left, that is, from the West terniinal'station. andsubstantially zero reception from the east. quency would be passed bythe filter FI and impressed upon the modulator Ml. Simultaneous with thereception of this sigzjnalinsf frequency, the modulatingl frequency AWould be transmitted by TA., and received by the antenna RA. Thisfrequency would be amplified by the amplier A., and impressed upon themodulator lvlp 0f the products of modulation, one frequency. namely, f1;would he selected by the filter F.. and impressed upon the an'iplitierAi. This frequency. when amplified. would be transmitted by the antennarlAr The transmitted frequency f1.: Wouldy be received by the antennaRA, of the repeater HB2 and iveuld be trans-lated therein as shown inFig. 8 to produce the frequency f5, Which Would be radiated from asimilar antenna as TAZ. In transmitting from the east terminal .tationtothe West, Waves of the fre-- quency f, would be impressed upon the receiving antenna BA.. and would be passed by the filter F2 to themodulator M. Herein they would be beaten With the frequency The receivedfrelll) A f1, and of the products of modulation one of the frequencies,namely, f2 would be selected by the filter F4 and amplified by theamplifierl A2. This frequency would then be transmitted by the antennaTAS and would be received by the antenna BA1 of the west terminalstation. By making the difference frequency f, sufiiciently large, thetransmitted frequency at any repeater will not enter the receiving`circuit at that station and consequently, singing thereat will beprevented. Furthermore, singing is prevented by the use ofdirection-controlled receiving antennae at the various stations, whichdiscriminate against waves coming` from directions other than that forwhich they are designed to loe selective. The distribution in Fig. 4differs from that in Fig. 3 in that, for example, at the repeater RR,the frequency ltransmitted to the west is more Widely separated from thefrequency received from the West than in Fig. 3. In Fig. 5 the receivedfrequency f2 is translated by an amount A f, to produce the frequency f5for transmission therefrom, the frequency f5 lying within the oppositeside band of the fictitious carrier frequency f to that side band inwhich the frequency f2 lies. In like manner, the received frequency f3is translated by the amount A f, to produce the frequency f., fortransmission. It will be seen, therefore, -that by means of thearrangement shown in Fig. l, operated in accordance with t-he frequencydistribution shown in Figs. 3 to 5 inclusive, a two-way communicationchannel may be established in a system employing a plurality ofrepeaters which does not require more than four frequencies per channelof communication, irrespective of the number of repeaters, .and which issubstantially free from singing.

While this invention has been disclosed as embodied in a particular formit is obvious that it is capable of embodiment in other forms withoutdeparting from the spirit and scope of the appended claims.

lhat is claimed is:

1. ln a radio repeating system having terminal stations and a pluralityof repeater stations located therebetween in which twoway signaling iseffected by using at each repeater stat-ion a transmitting wave ofdifferent frequency from the received Wave, the

method for limiting. the number of frequencies used throughout thesyst-em'for eac-h channel of communication to four regardless of thenumber of repeaters involved, which consists in receiving bydirectionally selecting at each repeater station east and west waves ofdifferent frequencies, translating each of the said frequencies by thesame amount and transmitting each of the said waves as thus changed.

2. In a radio repeating system having terminal stations and a pluralityof repeater stations located therebetween in which two way signaling iseffected by using at each repeater st-ation a transmitting wave ofdifferent frequency from the received wave, the method for limiting thenumber of frequencies used throughout the system for each channel ofcommunication to four regardless of the number of repeaters involved,which consists in receiving by directionally selecting at each repeaterstation east and west waves of diderent frequencies, receiving a carrierfrequency, beating each of the received frequencies by the said carrierfrequency, and selecting one side band of each received wave as thusbeaten, and transmitting each of the side bands as thus selected, thesaid beating frequency being so chosen that the sum of the said carrierfrequency and the lower received frequency will be lessthan thedifference of the carrier and the higher received frequency.

3. ln a radio repeatingsystem, the combination with a plurality ofterminal stations of a repeater station comprisingtwo directivereceiving antennae adjusted to receive from relatively oppositedirections, a plurality of transmitting antennae and a plurality oftranslating circuits, each connecting one receiving antenna with one ofthe transmitting' antennae, each translating circuit including amodulator interposed between a plurality of filters, a third receivingantenna adapted to receive a beating frequency, and means to apply thesaid beating frequency to the modulators of each of said tianslatingcircuits in order to demodulate the received frequencies presentin eachof the translating circuits.

In testimony whereof, I have signed my name to this specification this20th day of March, 1924.

DE LOSS K. MARTIN.

